1. Field of the Invention
This invention relates generally to measuring devices, and more particularly to a measuring device for measuring suspension sag of a vehicle.
2. Description of Related Art
The prior art teaches various devices for measuring the “sag” of a vehicle (i.e., the amount that the vehicle's suspension sinks under the weight of the vehicle and/or the rider). The “rider sag,” the amount that the motorcycle sinks under the weight of the rider, is particularly important to the performance of the vehicle, particularly a motorcycle. Adjusting the spring tension of the motorcycle to adjust the sag has an important impact on the performance of the motorcycle. The rider sag may need to be adjusted for different riders who are of different weights and/or have different riding techniques or preferences, and may even be adjusted by a single rider to adjust the motorcycle for a particular race, so that the motorcycle provides the most desirable handling characteristics for that race.
Most prior art measuring devices rely primarily on more or less directly measuring, with a ruler, tape measure, or similar device, the distance from a hub of a wheel to a reference point on a body of the vehicle. An example of such a method is shown in Schmidt, Jr. et al., U.S. Pat. No. 5,398,419. Disadvantages of this techniques include: 1) that it requires two people to perform the measurement; 2) that it requires recording and calculating the measurement; and 3) inconsistent measurements will occur because the user has to locate the measure points every time a measurement is made.
The state of the art device for use with motorcycles is Metcalf et al., U.S. Pat. No. 5,027,524, which teaches a suspension gauge that includes two telescoping element, and a ring that slides over one of the elements. Measurement markings are printed on one of the telescoping elements for measuring the movement of the ring, thereby enabling calculation of the sag. The initial position of the ring is first noted against the scale, and then the weight is applied to the vehicle (vehicle and/or rider), and the movement of the ring can be observed and measured relative to the starting position. Metcalf is somewhat difficult to use, however, and errors in calculations can lead to incorrect measurements of the vehicle's sag. The above-described references are hereby incorporated by reference in full.
The prior art teaches a suspension gauge that includes two telescoping elements that slide a measurement ring relative to markings on one of the telescoping elements. However, the prior art does not teach an even easier system that includes two telescoping elements that move a third ruler element, wherein the measurement markings are located on the third ruler element rather than one of the telescoping elements. The use of the ruler element makes the task of measuring sag extremely simple, with no need for any calculations whatsoever. Furthermore, the necessary measurement may be easily made by a single person, and without any room for error. The present invention fulfills these needs and provides further related advantages as described in the following summary.